Formed paper article, local region coating method, and coating device

ABSTRACT

A raised resin portion  8, 9  is formed by thermally spraying a powdered resin on a local portion such as a bonding step portion of a cup-shaped formed paper article  1  to improve sealing performance of the formed paper article and form a resin coating layer  60  including a scorching-preventing substance on a local region where scorching tends to occur during heating in a microwave oven. The raised resin portion is formed on the local region by intermittently discharging the resin powder from a tank with a shutter device and repeatedly thermally spraying the resin powder on the local region with a pressurized gas.

TECHNICAL FIELD

The present invention relates to a formed paper article such as acup-shaped formed paper container, and a local region coating method andcoating device suitable for coating with a coating material a localregion of the formed paper article.

BACKGROUND ART

In typical cup-shaped formed paper articles such as formed paperarticles for eating and drinking, there is a step created by bonding oftwo blank edges in an opening curled portion, a bonding portion is alsopresent at a body, and paper ends are exposed on the cup inside andoutside at the two edges of the bonding portion.

Where such a cup-shaped formed paper article is filled with contents andsealed, a lid is heat-sealed to the upper surface of the curled portion.Further, where the contents is to be consumed immediately after filling,for example, when the article is sold in a store, the article is soldwith an overcap fitted on and engaged therewith. When the lid isheat-sealed, the curled portion is usually crushed in a flat shape andflanged to increase the adhesion area in order to prevent defects inthermal adhesion of the lid. Such cup-shaped formed paper articles havebeen used as containers for direct drinking, but where a step portion ispresent at the opening end, it is uncomfortable for the lips, and theflange which has been crushed in a flat shape is itself uncomfortablefor the lips. Another problem is that since the paper edges are exposedinside and outside the formed article at the bonding position of thebody, in particular, the paper edge positioned on the inside is indirect contact with the liquid contents, absorbs moisture, and degradeswater resistance of the container. Yet another problem encountered inthe case of drawn paper articles is that since wrinkles are generated onthe flange portion of the opening peripheral edge, the sealingperformance is difficult to ensure when the lid is sealed to the flangesurface.

As a method for resolving the problems inherent to formed paper articleswhich are formed by bonding a blank, it has been suggested to provide anedge extension piece composed of a thermoplastic resin layer laminatedon a base material sheet at two opposing edges of the blank, bond twoend portions such that one edge extension piece comes to the inner sideand the other edge extension piece comes to the outer side of the formedpaper article so that the paper portions of the base material sheet donot overlap, and bond the edge extension pieces by thermocompression(see Patent Literature 1). Another suggested method involves scrapingthe side edge on the inner side to make it thinner toward the end sideand bonding the side edge on the outer side thereto to form a bodybonding portion and a curl bonding portion, thereby reducing in size thestep in the bonding portion (see Patent Literature 2). In yet anothersuggested method, a resin reinforcing ring which has been moldedseparately is welded to the opening to eliminate a step in the curledportion of the opening and improve the sealing performance and comfortfor the lips (see Patent Literature 3).

Meanwhile, in recent years, formed paper containers mainly composed ofpaper materials as recycling resources have attracted attention from thestandpoint of environmental load, and a demand has been created formicrowavable formed paper containers that have improved sealingperformance, can hold contents such as soups, beverages, and solidmatter, and can be heated in a microwave oven. However, where a formedpaper container having a blank bonding portion is heated in a microwaveoven, microwaves tend to concentrate in the bonding portion andscorching tends to occur in this part. In particular, a problemassociated with a cup-shaped formed paper container having an annularleg portion is that scorching tends to occur on the inner peripheralsurface of the annular leg portion.

Accordingly, formed paper containers configured to prevent theoccurrence of scorching during heating in a microwave, oven haveheretofore been suggested (see, for example, Patent Literature 4 and 5).However, the problems associated with the two conventional cup-shapedformed paper containers are that the bottom shape thereof is changed,the containers also have a complex structure, new production equipmentis needed to replace the conventional production line, and the cost isincreased.

Meanwhile, a method for coating a molten resin by discharging with a hotmelt gun or a hot liner has been generally used as a means for locallycoating the resin on an object such as the conventional formed papercontainers, but since the resin stringing phenomenon occurs after thedischarge from the nozzle, accurate coating on narrow regions aredifficult to implement, the resin is wasted, and cycle-up is difficult.Wet methods such as resin solution coating or emulsion coating are alsoknown, but problems associated with these methods include a limitednumber of materials suitable therefor, the necessity to vaporize asolvent after the coating, and a high environmental load created by thesolvent. A method has also been suggested by which a molten resinobtained by extruding and melting a resin starting material with a screwunder heating, in the same manner as in an injection molding machine, issprayed in the form of fine particles on the surface of an object suchas a metal to form a coating (see Patent Literature 6). Although such adevice is suitable for coating a resin on the surface of a large object,the resin is difficult to spray intermittently and accurately in verysmall amounts. For example, such a device is difficult to apply toforming a small raised resin portion on a step portion on an openingcurled portion of a paper cup or the like. Other problems are that thedevice is difficult to reduce in size and increase in speed and theequipment cost is high.

In yet another known method, an adhesive resin powder is coated on anobject surface with a thermal spraying gun by flame spraying that usesflame obtained with acetylene, propane, and the like (see PatentLiterature 7). However, in this case, the intermittent processing andspray pattern control are difficult, thermal spray coating is difficultto perform reliably on narrow regions, and the object or the coatingresin itself can be thermally degraded by the flame.

Thus, it can be said that an accurate and efficient technique forintermittently and locally forming a resin coating on a narrow regionhas not yet been established with respect to products that are conveyedon a conveyor line and produced industrially on a large scale.

PRIOR ART LITERATURE Patent Literature

Patent Literature 1: Japanese Patent Application Publication No.2005-14975

Patent Literature 2: Japanese Patent Application Publication No.2003-191941

Patent Literature 3: Japanese Patent Application Publication No.2002-264918

Patent Literature 4: Japanese Patent Application Publication No.2003-95352

Patent Literature 5: Japanese Patent Application Publication No.2005-88955

Patent Literature 6: Japanese Patent Application Publication No.H09-201833

Patent Literature 7: Japanese Patent Application Publication No.S63-141666

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

The problems arising when the bonding end portion is formed of edgeextension pieces composed of a thermoplastic resin, or the thickness ofthe paper edge is decreased to reduce the bonding step in size, asdescribed in Patent Literature 1 and 2, in the conventional formed paperarticles are that processing is difficult and unstable and themanufacturing process becomes complex. Further, the speed and efficiencyof the manufacturing process are difficult to increase. Where an openingreinforcing resin ring is fused, as a separate member, to a formed paperarticle, the material cost is increased and processes of molding andwelding a resin ring are required separately. Hence, problems such as anincrease in production costs arise.

Further, it can be said that an accurate and efficient technique forintermittently and locally forming a resin coating mainly composed of asynthetic resin on a narrow region of a formed paper article has not yetbeen established with respect to formed paper articles that are conveyedon a conveyor line and produced industrially on a large scale.

Accordingly, it is an objective of the present invention to provide aformed paper article which can resolve the above-described problems offormed paper articles in a simple manner and without a complex processand in which the problems associated with sealing performance, bondingportion, and the occurrence of wrinkles in formed paper articles havingan opening are resolved, and also to provide a local region resincoating method and a device therefor that enable accurate and efficientresin coating even on a narrow region of the formed paper article andalso enable intermittent and repeated resin coating.

Means for Solving the Problems

The formed paper article of the present invention that resolves theabovementioned problems is a formed paper article having an opening,wherein a raised resin portion is molded on a local portion by thermallyspraying a coating material configured of a powder mainly composed of asynthetic resin.

The formed paper article of the present invention can be configured suchthat the local portion is at least a bonding step portion of aperipheral edge of the opening of a cup-shaped formed paper article, andthe raised resin portion is formed on the step portion to bury the stepportion.

The configuration can be also such that where the local portion is abonding step portion of the body of the formed paper article, a paperedge in the bonding portion is coated with resin by forming a raisedresin portion on the step portion.

The configuration can be also such that where the formed paper containeris a drawn article mainly composed of paper, wrinkles on an openingflange surface are coated by forming the raised resin portion on anentire periphery of the opening flange surface.

The configuration can be also such that the raised resin portion ismolded by thermally spraying a heat-adhesive resin powder and has acoating thickness of 0.3 mm or less.

Where the formed paper container of the present invention is adapted toheating in a microwave oven, the occurrence of scorching duringmicrowave heating can be prevented by forming a resin coating layerincluding a scorching-preventing substance on a local region of thepaper container.

In the case of a cup-shaped formed paper container, the local region isan inner peripheral surface of an annular leg portion where scorchingtends to occur during heating in a microwave oven.

By forming the resin coating layer by thermally spraying a powder inwhich a scorching-preventing substance powder is mixed with a resinpowder, it is possible to form the coating layer effectively with asmall amount of a coating material at a predetermined position.

The type of the resin powder is not limited, and a polyolefin resinpowder such as polyethylene and polypropylene or a polyester resinpowder such as PET, PEN, PLA, and PBT with a particle diameter of 30 μmto 300 μm can be effectively used.

Meanwhile, calcium carbonate or talc, which is an inexpensive substancewith a low dielectric constant, can be used as the scorching-preventingsubstance powder.

The local region resin coating method of the present invention thatresolves the abovementioned problems is a coating method for coating alocal region of an object with a coating material mainly composed of asynthetic resin, wherein a powder mainly composed of the synthetic resinis intermittently thermally sprayed on the local region.

Where the powder is quantitatively discharged, pumped with a pressurizedgas, merged with a heating gas and intermittently thermally sprayed onthe local region, quantitative resin coating of the object can beperformed repeatedly by small amounts.

The heating is preferably such that the powder is heated by hot airclose to a melting point of the synthetic resin and partially melted.Where the local region of the object which is to be coated is preheated,the resin powder is not sprayed in a completely molten state, and thesprayed resin powder is completely melted on the object surface to coatthe object surface. Therefore, the stringing phenomenon does not occur,cycle-up of intermittent thermal spraying is enabled, and coatingefficiency can be increased.

The local region resin coating device of the present invention thatresolves the abovementioned problems is a coating device for coatingwith a coating material mainly composed of a synthetic resin, thecoating material being a powder and the coating device including a tankfor supplying the powder, a thermal spray nozzle communicating with alower end of the tank, and a quantitative discharge shutter deviceprovided between a lower end opening of the tank and the thermal spraynozzle, wherein the powder is quantitatively discharged from the tank bythe quantitative discharge shutter device, merged with a heating gas,and thermally sprayed from the thermal spray nozzle.

A configuration can be used in which the quantitative discharge shutterdevice is composed of a rotating body provided across an outlet openingof the tank, a metering chamber facing the outlet opening of the tank isprovided in the rotating body, a valve is provided that communicateswith a gas supply port of the metering chamber and supplies apressurized gas to the metering chamber, the rotating body can berotated intermittently between a metering position and a thermalspraying position, at the metering position, the powder isquantitatively metered facing the outlet opening of the tank, at thespraying position, the metering chamber faces the thermal spray nozzle,the pressurized gas is supplied from the valve to the metering chamber,and the powder is pumped into the thermal spray nozzle.

Advantageous Effects of the Invention

According to the present invention, as a result of simply forming araised resin portion locally on a formed paper article, the problemsassociated with the bonding portion and the occurrence of wrinkles informed paper articles having an opening are resolved easily and at a lowcost, without subjecting the base blank material to special processing,and a formed paper product with excellent sealing performance can beobtained.

Further, as a result of applying the present invention to the bondingstep portion on the opening peripheral edge of a cup-shaped formed paperarticle and forming a small raised resin portion on the step portion, itis possible to improve comfort for the lips when drinking the contentsdirectly from the container, improve sealing capability at the stepportion when heat-sealing the lid and improve the sealing performance.Furthermore, applicability of the formed paper article to sealedcontainers in which the contents can be stored at a normal temperaturecan be increased. In addition, leak from the step portion can beeffectively prevented when the container is covered with an overcap andsealed.

The present invention can be also applied to an exposed paper edge suchas the bonding portion of a formed paper article, thereby making itpossible to coat the exposed paper edge effectively with a resin,prevent moisture absorption from the contents, or the like, from theexposed paper edge, and improve water resistance.

Further, by applying the present invention to an opening flange surfaceof a drawn article mainly composed of paper, it is possible to cover thewrinkles on the flange, increase thermal welding ability of theheat-seal lid, and improve sealing performance.

With the configuration such that the raised resin portion is formed bythermally spraying a heat-adhesive resin powder and has an averagecoating thickness of 0.3 mm or less, the raised resin portion can beformed efficiently from a small amount of a resin material and withoutstringing.

When the formed paper container of the present invention is adapted toheating in a microwave oven, as a result of forming a resin coatinglayer including a scorching-preventing substance on the local regionthereof, the occurrence of scorching during microwave heating can beeasily prevented by a simple means, without changing the basic structureof the conventional formed paper container.

In the case of a cup-shaped formed paper container, by only forming aresin coating layer including a scorching-preventing substance on theinner peripheral surface of an annular leg portion, it is possible toprevent easily the occurrence of scorching, without changing the bottomshape of the conventional cup-shaped formed container.

Further, as a result of forming the resin coating layer by thermallyspraying a powder in which a scorching-preventing powder is mixed with aplastic powder, the scorching-preventing layer can be formed reliablyand inexpensively on the inner peripheral surface of the annular legportion. By using an inorganic substance with a relative dielectricconstant of 2 or less as the scorching-preventing substance powder, itis possible to form the scorching preventing layer effectively.

With the coating method of the present invention, by intermittentlythermally spraying a powder mainly composed of a synthetic resin on alocal region, it is possible to coat the resin accurately andefficiently even on a small area.

Since the powder mainly composed of a synthetic resin is dischargedquantitatively and intermittently and thermally sprayed, a material witha small particle diameter and a high welding efficiency can be thermallysprayed on a small area, resin coating can be performed efficiently byusing a minimum amount of material, and high cycling is made possible.

Further, with thermal fusion, since the synthetic resin powder is heatedby hot air close to the melting point thereof and partially melted, thepowder melts after adhesion to the object. Therefore, the resinstringing phenomenon is eliminated and high-speed intermittent sprayingcan be accurately performed.

As a result of preheating the local region of the object which is to becoated with the resin, the resin powder which is thermally sprayed in astate of being heated close to the melting point thereof and partiallymelted can be efficiently welded to the local region.

Further, by applying the coating method of the present invention to thebonding step portion on the opening curled portion of a container havingan opening, a small raised resin portion can be formed on the stepportion, comfort for the lips can be improved when drinking the contentsdirectly from the container, and sealing capability at the step portionwhen heat-sealing the lid can be improved. Further, leak from the stepportion can be effectively prevented when the container is covered withan overcap and sealed.

By applying the coating method of the present invention to an exposedpaper edge such as the overlapping portion of a formed paper container,it is possible to coat the exposed paper edge effectively with a resin,prevent moisture absorption from the contents, or the like, from theexposed paper edge, and improve water resistance.

Further, by applying coating method of the present invention to a formedpaper article of a low rigidity, it is possible to add local increase inthickness as reinforcement and increase the rigidity and shape retainingability of the formed article.

Furthermore, for example, by mixing a powder of an inorganic substance,or the like, with the powdered resin and applying the coating method ofthe present invention to a location where scorching tends to occur whena paper container is heated in a microwave oven, the location can bemodified such that scorching is unlikely to occur.

The coating device of the present invention has a simple configuration,can be reduced in size, can be easily and inexpensively incorporated inthe usual production line, enables accurate and intermittent thermalspraying of a small amount of a powdered resin even when the thermalspraying region has a small area, and makes it possible to reduce theamount of material used.

Further, as a result of providing the coating device of the presentinvention with the quantitative discharge shutter device, it is possibleto perform accurate metering with a simple mechanism even with smallamounts of the powdered resin, and also intermittently and at a highspeed. As a consequence, a powder with a small particle diameter thathas poor sliding ability can be also used.

Further, by using a heating gas as hot air, thermal spraying can beperformed without using a flame, and thermal effects on the object andthe coating resin itself can be mitigated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view and partial cross-sectional views of theformed paper container according to an embodiment of the presentinvention.

FIG. 2 shows a perspective view of the formed paper container accordingto another embodiment of the present invention.

FIG. 3 shows schematic view illustrating the principal part of thecoating device and the coating method according to an embodiment of thepresent invention.

FIG. 4 shows schematic views illustrating how the metering chamber iscompression filled with the powder in the device depicted in FIG. 3.

FIG. 5 shows photos illustrating the raised resin portion formed on alaminated source paper of Example 1 of the present invention.

FIG. 6 shows photos of the cross section and top surface of the stepportion after a raised resin portion has been formed on the step portionin Example 2 of the present invention.

FIG. 7 illustrates a preheating process and a thermal spraying processof the coating method according to an embodiment of the presentinvention.

EXPLANATION OF REFERENCE NUMERALS

-   1 cop-shaped container-   2 body-   3 opening curled portion-   4 step portion-   5 body bonding portion-   6 paper edge-   7 annular leg portion-   8, 9, 13 raised resin portions-   10 drawn container-   12 flange surface-   14 wrinkles-   25 preheating nozzle-   30 coating device-   31 tank-   32 thermal spray nozzle-   33 lower end opening-   34 powder supply device-   35 quantitative discharge shutter device-   36 rotating body-   37 metering chamber-   38 gas supply port-   40 hot air generator-   42 flow channel-   43 supply conduit-   44 electromagnetic valve-   45 introducing flow channel-   46 spraying flow channel-   52 folded piece-   57 bottom plate-   58 annular curved portion-   60 layer of resin mixed with inorganic substance-   70 trial laminate source paper-   71 raised resin portion

MODES FOR CARRYING OUT THE INVENTION

An embodiment of the formed paper container according to the presentinvention will be explained hereinbelow in greater detail with referenceto the drawings.

FIG. 1 illustrates a cup-shaped container as a formed paper bodyaccording to an embodiment of the present invention. In the cup-shapedcontainer 1, a conical shape is molded by adhesively bonding both edgesof a fan-shaped blank serving as a body 2, the upper end portion of theconical shape is curled to form an opening end portion, an annular legportion 7 is obtained by folding a step surface at a lower end B inward,as depicted in (d) in FIG. 1, to form a folded piece 52 and crimping anannular curved portion 58 of a bottom plate 57, which has been drawn tohave a U-shaped cross section, between the lower end and the foldedpiece, and a step portion 4 produced by bonding the two edges of theblank is made, as shown on an enlarged scale in (b) in FIG. 1, in aportion A of the opening curled portion 3. Further, a bonding portion 5is formed in the body, and the paper ends are exposed on the inside andoutside of the cup at both edges of the bonding portion. Theabove-described structure is the same as that of the conventionalwell-known cup-shaped formed paper container.

In order to prevent the above-described sealing defects caused by thestep portion 4 in the opening curled portion 3 at the opening peripheraledge of such a cup-shaped formed paper container and avoid discomfortfor the lips when the container is used as a direct drinking container,in the present invention, a raised resin portion 8 was formed bythermally spraying a small amount of a synthetic resin on the stepportion and the step was buried in the resin.

A raised resin portion is difficult to form with precision on a narrowregion such as the step portion 4 of the curled portion of thecup-shaped formed paper container, but in the present embodiment, theraised resin portion could be satisfactorily formed on the step portion4 of the curled portion by intermittently thermally spraying a powderedresin with a resin thermal spraying device shown schematically in FIG.3, and the aforementioned problems could be resolved by a simple method,without special processing of the source paper edges themselves.

Further, in the present embodiment, as shown on an enlarged scale in (c)in FIG. 1, the paper edge 6 exposed on the inner surface side was coatedwith a resin by forming a continuous raised resin portion 9 in thevertical direction along the paper edge 6, in particular on the innersurface side of the cup, of the body bonding portion 5 in the formedpaper container. As a result, the paper edge 6 was prevented form cominginto direct contact with liquid contents and moisture resistance of thecontainer could be increased. Further, in the present embodiment, theresin was coated only on the paper edge on the inner side of the bondingportion, but it is preferred that the outer side be likewise also coatedwith the resin.

Where such a formed paper container is to be adapted to heating in amicrowave oven, both the body blank material and the bottom material aremainly composed of paper, but the inner and outer surface are laminatedor coated with a polyolefin resin, a polyester resin, etc. forprotection from liquid contents, or an impregnated composite papermaterial or a multilayer material optionally having a gas barrier layeras the inner layer can be used. The materials to be used are notparticularly limited, provided that they can be heated in a microwaveoven.

In the cup-shaped container described hereinabove, in the presentembodiment, a resin coating layer 60 including a scorching-preventingsubstance was formed, as depicted in (d) in FIG. 1, on the entireperiphery of the inner peripheral surface of the annular leg portion 7where scorching tends to occur during heating in a microwave oven, andthe occurrence of scorching during heating in a microwave oven wasprevented. In the present embodiment, the resin coating layer 60 wasformed on the inner peripheral surface of the annular leg portion 7 bythermally spraying a powder with a particle diameter of 30 μm to 300 μmin which a synthetic resin powder was mixed with thescorching-preventing substance powder.

The powders that can be used in the present invention include, but arenot limited to, materials which are easily adhesive to formed papercontainers mainly composed of paper. In a typical formed papercontainer, a paper base material serving as a base is coated with aresin, and in order to ensure easy adhesion, it is preferred that aresin of the same type as the surface resin layer, or a resin with amelting point lower than that of the surface resin layer be used.

Here, the synthetic resin is not particularly limited, provided it is athermoplastic resin, and a single resin powder or a plurality of resinpowders selected from polyolefins such as high-medium-low-densitypolyethylene and polypropylene and polyesters such as PET, PEN, PLA, andPBT can be used. Further, for example, calcium carbonate and talc, whichare substances with a low relative dielectric constant, can be used asthe scorching-preventing substance. As a result generation of heatcaused by absorption of microwaves in the annular leg portion can bereduced and the occurrence of scorching can be prevented.

Methods using hot melting, a hot runner, flame thermal spraying, etc.,can be considered for forming a resin coating layer including ascorching-preventing substance on the local region. However, when any ofthe above-mentioned methods is used to form the resin coating layer on avery narrow coating region by using a small amount of resin on ahigh-speed container production line, as in the present embodiment, acoating resin stringing phenomenon occur, a restriction is placed oncycle-up, and accurate coating is difficult to perform. To overcome thisproblem, in the present embodiment, a preheating process and a resinthermal spraying process were provided for post-processing a cup-shapedcontainer which was formed and conveyed in a production line, hot airwas blown onto the resin coating region in the preheating process topreheat the inner peripheral surface of the annular leg portion close tothe melting point of the coating resin, and then the resin powder wasthermally sprayed on this portion in the resin thermal spraying process.As mentioned hereinabove, thermal spraying of the resin powder can beperformed by using, as a starting material, a powdered resin powder witha particle diameter of 30 μm to 300 μm in which a synthetic resin powderis mixed with a scorching-preventing substance powder, andintermittently or continuously thermally spraying the starting materialon the inner peripheral surface of the annular leg portion with athermal spray nozzle by using a pressurized heating gas (in the presentembodiment, the hot air) heated to or below the melting temperature ofthe resin, thereby forming a raised resin portion.

By coating the resin on the inner peripheral surface of the annular legportion by the above-described method, it is possible to coat the resinwith precision on a predetermined small region without the occurrence ofthe stringing phenomenon, and the amount of the material used can beminimized.

FIG. 2 illustrates another embodiment of the present invention. In thepresent embodiment, a raised resin portion 13 was formed on a flangesurface 12 of a drawn container 10 on the entire periphery of the flangeso as to cover wrinkles 14 on the flange surface which appeared in thedrawing process (in FIG. 2, the raised resin portion is formed on halfof the flange surface), and when a lid was heat-sealed, the resin fusedand buried the wrinkles, the lid was perfectly fused, and the sealingperformance was improved.

As mentioned hereinabove, when a small raised resin portion is formed ona local narrow region of a formed paper container, stringing of theresin occurs, the raised resin portion is difficult to form efficientlyand over a short period of time only in the predetermined location, andthe resin is wasted. However, in the present embodiment, byintermittently thermally spraying a powdered resin by using thebelow-described resin coating device, it was possible to coat the resinwith precision on the predetermined small region, without the occurrenceof the stringing phenomenon, and the amount of the material used couldbe minimized.

Embodiments of the coating method and coating device of the presentinvention that make it possible to form accurately a small raised resinportion locally on the formed paper container will be describedhereinbelow in detail with reference to FIG. 3 and FIG. 4.

As a method of the present invention that enables high-speed reliableresin coating, without the occurrence of the stringing phenomenon or thelike, with a small amount of resin on a small region of an object, inthe present invention, a powder mainly composed of a synthetic resin wasquantitatively discharged, heated close to the melting point of thesynthetic resin, and intermittently and repeatedly thermally sprayed onthe local region. A resin material and a particle diameter thereof areselected for the synthetic resin powder according to the application andtarget of the location to be coated with the synthetic resin. Forexample, when thermal spraying is performed to form a raised resinportion on the opening curled portion of the cup, a heat-sealable resinpowder such as polyethylene is used in order to eliminate the stepportion, improve comfort for the lips, heat seal with the lid, andimprove the sealing performance.

FIG. 3 illustrates schematically the principal part of a resin coatingdevice 30 according to the present embodiment which serves for thermallyspraying a powdered resin on a local region. In the device, a thermalspray nozzle 32 is provided at a lower end opening 33 of a hopper-shapedtank 31, with a quantitative discharge shutter device 35 beinginterposed between the nozzle and the opening. A powder supply device 34for supplying a powder mainly composed of a resin to the tank is linkedto the tank 31. Further, if necessary, a heating means can be alsoprovided for heating the supplied powdered resin to a predeterminedtemperature. A hot air generating device 40 is preferred as the heatingmeans.

The quantitative discharge shutter device 35 is composed of a rotatingbody 36 provided across the lower end opening 33 of the tank 31, and ametering chamber 37 facing the lower end opening 33 of the tank 31 isprovided in the rotating body 36, the metering chamber being in the formof a conical recess such that the top portion thereof reaches thesubstantially central axis of the rotating body 36. One end of therotating body 36 is linked to an intermittent rotary drive means (notdepicted in the figure). The rotating body has a flow channel 42 alongthe central axis thereof, the flow channel being connected at one end toa pressurized gas source and communicating with a pressurized gas supplyport 38 formed in the top portion of the metering chamber 37. A supplyconduit 43 linked to a compressed air supply source such as a compressoris linked to the flow channel 42, and the delivery timing of thepressurized gas into the metering chamber 37 is controlled by anelectromagnetic valve 44 provided in the supply conduit. The rotatingbody 36 is half-turned intermittently and controlled such that themetering chamber is alternately positioned at a powder metering positionand a position of pumping to the thermal spray nozzle.

A heating gas is supplied as a heating means to the thermal spray nozzle32. Hot air is preferred as the heating gas, and the hot air is suppliedby a hot air generator 40, which is linked to the air supply source suchas a compressor, to the thermal spray nozzle as a heating gas heated toa predetermined temperature by a heating means such as electricalheating or gas combustion.

The thermal spray nozzle 32 has at the top portion thereof anintroducing flow channel 45 capable of receiving the powdered resin fromthe metering chamber 37 when the rotating body 36 is rotated to thethermal spraying position, and a spraying flow channel 46 with apredetermined port diameter is formed below the introducing flowchannel. The heating gas is supplied to the spraying flow channel 46,and the heating gas merges with the powder pumped from the meteringchamber. Naturally, the rotating body 36 is rotatably linked in a sealedstate such that the powder does not leak to the outside between the tank31, the quantitative discharge shutter device 35, and the thermal spraynozzle 32.

The device for coating a powdered resin of the present invention has theabove-described configuration and forms a resin coating by thermallyspraying the powdered resin in the below-described manner on the localregion of an object.

Initially, the region of the object which is planned to be coated withthe resin is preheated. A method for preheating is not particularlylimited, and a variety of heating methods can be used, but a method forblowing hot air from a preheating nozzle 25, such as illustrated by (a)in FIG. 7, is preferred since heating can be performed locally in asimple manner with an inexpensive equipment. The preheating can be alsoperformed by using hot air from the thermal spray nozzle and delayingthe spraying of the resin. As a result of preheating the thermalspraying target surface, the resin can be satisfactorily welded to theobject surface even when the resin sprayed from the thermal spray nozzleis not completely melted, and the resin coating can be formedintermittently and at a high speed.

The preheated local region of the object is then coated with the resinby thermally spraying the powdered resin with the abovementioned coatingdevice. In thermal spraying of the powdered resin with the device, thepowdered resin is supplied into the tank 31 in the state depicted in (a)in FIG. 3, and in this state, the powdered resin of a volume equal tothat of the metering chamber is automatically loaded into the meteringchamber 37 of the quantitative discharge shutter device 35. The rotatingbody 36 is then rotated through 180°. As a result, as depicted in (b) inFIG. 3, the metering chamber 37 is inverted to face the introducing flowchannel 45 of the thermal spray nozzle 32. At the same time, the valve44 is opened, the pressurized gas is blown through the pressurized gassupply port 38 into the inverted metering chamber, the metered amount ofthe resin powder in the metering chamber is merged with the heating gasflowing through the spraying flow channel 46 of the thermal spray nozzleand thermally sprayed on the local region of the object ((c) in FIG. 3).Thus, in the present embodiment, as a result of repeating theabovementioned operations and intermittently thermally spraying a smallamount of the powdered resin a plurality of times on the same zone, forexample, after the object has been stopped, it is possible to formreliably a raised portion including a predetermined amount of resin in avery narrow range. With the method of the present invention, since theresin is thermally sprayed intermittently in small amounts, thethermally sprayed resin is in a partially melted state and can be meltedon the object surface and fused thereto, and fusion defects can beprevented. Further, the surface of the formed raised resin portion canbe made smoother by reheating.

When the particle diameter of the resin powder is small and the resinpowder has poor sliding ability, a nozzle 34-1 of the powder resinsupply device 34 provided inside the tank is extended close to the topof the metering chamber, as depicted in (b) in FIG. 4, to performcompression loading of the powder such that the inside of the meteringchamber 37 is completely filled with the resin.

EXAMPLES Example 1 Formation of Raised Resin Portion on Laminated SourcePaper

As depicted in FIG. 5, a powdered resin was thermally sprayed under thefollowing conditions by using the abovementioned device on a face sideof a trial laminated source paper 70 ([face] polyethylene 18 μm/sourcepaper (300 g/m²)/[back] polyethylene 18 μm).

Powdered resin: low-density polyethylene powder with an average particlediameter of 120 μm

Amount of powder sprayed in one cycle: about 20 mg

Distance between the thermal spray nozzle and thermal spray targetsurface: 6 mm

Temperature of hot air at the nozzle outlet: 320° C.

Preheating: delay before spraying 1.5 s

As a result, a raised resin portion 71 with a coating film thickness of1.1 mm in the central portion, such as depicted in FIG. 5, could besatisfactorily formed, without the occurrence of the stringingphenomenon.

Example 2 Formation of Raised Resin Portion on Step Portion

A resin was thermally sprayed under the following conditions with theabovementioned device close to the step portion 4 of the opening curledportion 3 of the cup-shaped container 1.

Powdered resin: low-density polyethylene powder with an average particlediameter of 12.0 μm

Amount of powder sprayed in one cycle: about 25 mg

Distance between the thermal spray nozzle and thermal spray targetsurface: 1.0 mm

Temperature of hot air at the nozzle outlet: 320° C.

Preheating: delay before spraying 1.5 s

Note: reheating was performed with a hot air generator.

As a result, a raised resin portion 8 with a coating film thickness of0.3 mm could be satisfactorily formed to cover the step portion 4, asdepicted in (b-1) in FIG. 6.

By forming the raised resin portion on the step portion in theabove-described manner, it was possible to improve weldability with thelid even without melting the resin or collapsing the curled portion whenthe lid was heat-sealed, the sealing performance could be improved, anddiscomfort during direct drinking could be eliminated. Also, in the caseof an overcap, since the step portion in the curled portion iseliminated, leakage therefrom can be prevented.

Example 3 Resin Coating for Local Improvement of the Object

A resin was coated under the following conditions over the entireperiphery of the inner peripheral surface of the annular leg portion ofthe cup-shaped container.

Tested container: cup-shaped container (material: the same in the bodyand bottom)

Material layer configuration:

-   -   Body: (inside) polyethylene (20 μm)//slush slush paper (250        g/m²)    -   Bottom: (inside) polyethylene (40 μm)//paper 250        g/m²//polyethylene (15 μm)

Full amount of contents: 565 ml, height of annular let portion: 10 mm

Thermal spraying conditions:

-   -   Powdered resin: powdered polyethylene with an average particle        diameter of 120 μm    -   Scorching-preventing substance (material with a low dielectric        constant): calcium carbonate

Resin coating film: width about 10 mm along the entire periphery of theinner periphery of the annular leg portion, coating thickness 1 mm orless

A resin coating layer including the scorching-preventing substance wasformed in the above-described manner on the inner peripheral surface ofthe annular leg portion. The following test was performed to verify theoccurrence of scorching in the cup-shaped container.

Container filling contents: water 330 ml

Output of microwave oven: 500 W

Heating time: 6 min

The abovementioned heating conditions correspond to the usual heatingtemperature which is optimum for eating the contents (noodle food).

Occurrence of scorching: in the container of the present example inwhich the coating layer was formed, the color of scorching whichoccurred at the bottom rim was lighter and the range thereof wasnarrower than in a comparative container which was not provided with thecoating layer.

Embodiments and examples of the microwavable formed paper container ofthe present invention are explained hereinabove, but the presentinvention is not limited thereto. Thus, the formed paper container ofthe present invention is not limited to cup-shaped containersnecessarily having an annular leg portion, and the present invention isalso applicable to various structures of microwavable formed papercontainers having a part where scorching tends to occur.

INDUSTRIAL APPLICABILITY

With the present invention, a raised resin portion can be formedreliably and efficiently on a narrow local region in a formed papercontainer, problems associated with sealing performance of the formedpaper container and the occurrence of scorching in heating in amicrowave oven can be resolved with a simple configuration,applicability of the formed paper container to normal-temperaturedistribution can be improved with an inexpensive configuration, and acoating resin can be reliably thermally sprayed on a local region. Thus,the present invention has high industrial applicability.

1. A formed paper article having an opening, wherein a raised resinportion is formed on a local portion by thermally spraying a coatingmaterial configured of a powder mainly composed of a synthetic resin. 2.The formed paper article according to claim 1, wherein the local portionis at least a bonding step portion of a peripheral edge of the openingof a cup-shaped formed paper article, and the step portion is buried bythe raised resin portion.
 3. The formed paper article according to claim1, wherein the local portion is a bonding step portion of a body of theformed paper article, and a paper edge in the bonding portion is coatedwith the raised resin portion.
 4. The formed paper article according toclaim 1, wherein the formed paper article is a drawn article mainlycomposed of paper, the local portion is an entire periphery of anopening flange surface, and wrinkles on the opening flange surface arecoated by the raised resin portion.
 5. The formed paper articleaccording to claim 1, wherein the raised resin portion is formed bythermally spraying a heat-adhesive resin powder and has an averagecoating thickness of 0.3 mm or less.
 6. The formed paper articleaccording to claim 1, wherein the formed paper article is a formed papercontainer adapted to heating in a microwave oven, wherein a resincoating layer including a scorching-preventing substance is formed on alocal region of the formed paper container.
 7. The formed paper articleaccording to claim 6, wherein the resin coating layer is formed bythermally spraying a powder in which a scorching-preventing substancepowder is mixed with a resin powder.
 8. The formed paper articleaccording to claim 7, wherein the scorching-preventing substance powderis an inorganic substance with a relative dielectric constant of 2 orless.
 9. A coating method for coating a local region of an object with acoating material mainly composed of a synthetic resin, wherein thecoating material is a powder mainly composed of a synthetic resin, andthe powder is intermittently thermally sprayed on the local region. 10.The coating method according to claim 9, wherein in the thermalspraying, the powder is quantitatively discharged, pumped by apressurized gas, merged with a heating gas, and intermittently thermallysprayed on the local region.
 11. The coating method according to claim10, wherein the heating gas is hot air, heats the synthetic resin powderclose to a melting point, and partially melts the powder.
 12. Thecoating method according to claim 9, wherein the local region to becoated in the object is preheated.
 13. A coating device for coating alocal region of an object with a coating material mainly composed of asynthetic resin, wherein the coating material is a powder, the coatingdevice comprises a tank for supplying the powder, a thermal spray nozzlecommunicating with a lower end of the tank, and a quantitative dischargeshutter device provided between a lower end opening of the tank and thethermal spray nozzle, and the powder is quantitatively discharged fromthe tank by the quantitative discharge shutter device, merged with aheating gas, and thermally sprayed from the thermal spray nozzle. 14.The coating device according to claim 13, wherein the quantitativedischarge shutter device is composed of a rotating body provided acrossan outlet opening of the tank, a metering chamber facing the outletopening of the tank is provided in the rotating body, a valve isprovided that communicates with a gas supply port of the meteringchamber and supplies a pressurized gas to the metering chamber, therotating body can be rotated intermittently between a metering positionand a thermal spraying position, at the metering position the powder isquantitatively metered facing the outlet opening of the tank, at thespraying position, the metering chamber faces the thermal spray nozzle,the pressurized gas is supplied from the valve to the metering chamber,and the powder is pumped into the thermal spray nozzle.